FIG. 1 illustrates a prior art assembly 100 including an integrated circuit 102 (illustrated as a “flip chip”) with an active surface 104 that is physically and electrically attached to a connection surface 106 of a carrier substrate 108 by a plurality of interconnects 112. Such interconnects 112 extend between bond pads 114 on the active surface 104 of the integrated circuit 102 and landing pads 116 on the connection surface 106 of the carrier substrate 108. Finally, an underfill material 118 may be disposed between the active surface 104 of the integrated circuit 102 and the connection surface 106 of the carrier substrate 108 to prevent contamination and to increase mechanical reliability.
In the past, such interconnects 112 comprised solely of solder material. However, recent designs have replaced such solder material, at least in part, with projections to improve bump pitch (e.g. the center-to-center distance between interconnects 112, etc.). More information regarding such interconnects 112 will be set forth during the description of FIG. 2.
FIG. 2 illustrates a single interconnect 112 including a metal projection 201, in accordance with the prior art. Such metal projection 201 may take various forms, such as a copper column, and may be formed on the bond pad 114 of the integrated circuit 102. The metal projection 201 is used for achieving a sufficient current flow through each interconnect 112 and to further reduce bump pitch, as mentioned earlier. As shown, the interconnect 112 still employs some solder material 202 to attach the metal projection 201 to the corresponding landing pad 116 of the carrier substrate 108.
As is known in the art, a photoresist mask 204 is typically patterned to contain the solder material 202, prior to the attachment of the metal projection 201 to the corresponding landing pad 116. Despite such containment, the solder material 202 still protrudes in the manner shown (see item 206), thus augmenting the aforementioned bump pitch in an undesirable manner.